Thread: GetProcAddres fails

Hi all,

I'm porting some project from mingw to MSVC. I managed to get everything to compile and link, but one problem remains: from the main application i have to load some DLL at run time and get the address of a function from it.
This is my loader code (taken from MSDN):

Code:

#include <string>
#include <iostream>
#include <windows.h>

int main()
{

	

	typedef const std::pair<const int, const std::string> (*LPFNDLLFUNC1)();


	HINSTANCE hDLL;               // Handle to DLL
	LPFNDLLFUNC1 lpfnDllFunc1;    // Function pointer
	DWORD dwParam1;
	UINT  uParam2, uReturnVal;

	hDLL = LoadLibrary("FennekEntity");
	if (hDLL != NULL)
	{
	   lpfnDllFunc1 = (LPFNDLLFUNC1)GetProcAddress(hDLL, "getUserType");
	   if (!lpfnDllFunc1)
	   {
		  // handle the error
		  FreeLibrary(hDLL);
		  std::cout << "getadd error" << std::endl;
	   }
	   else
	   {
		  // call the function
		  //uReturnVal = lpfnDllFunc1(dwParam1, uParam2);
	   }
	}
	else
	{
		std::cout << "loadlib error" << std::endl;
	}


	return 0;
}

And this is the code inside the DLL:

Code:

// FennekEntity.h



#ifdef FENNEKENTITY_EXPORTS
#define FENNEKENTITY_API __declspec(dllexport)
#else
#define FENNEKENTITY_API __declspec(dllimport)
#endif


#ifndef FENNEKENTITY_H_
#define FENNEKENTITY_H_

[...]

FENNEKENTITY_API const std::pair<const int, const std::string> getUserType();


#endif /*FENNEKENTITY_H_*/




// FennekEntity.cpp



#include "FennekEntity.h"

[...]

//extern "C"
//{

	
	

FENNEKENTITY_API const std::pair<const int, const string> getUserType()
{
	[...]	
}
	



//} // extern "C"

Does anybody has an idea, why getProcAddress always returns NULL? Using mingw it works (if I comment in the extern "C"). MSVC compains what an extern "C" declared function can't return non-pod data types, so I took it out.

Thank you in advance!

Thank you matsp. The problem seems to be the extern "C" linkage. If I take that out, run time loading does also fail with mingw.

So the correct question should probably be: How can I get MSVC to compile the DLL functions with extern "C" linkage, if that functions returns non-pod types/classes ?

The other solution is of course to use MingW instead of MSVC - but I suspect that this is not a solution you want to have, as I would guess that the reason you want MSVC may be that it's your corporate standard or some such.

In future I have to interface some extern code only available for MSVC. So I'm spending my nights learning about the littly but nasty compiler differences between mingw/gcc/msvc.

Thank you, you guys here are just the best and saved me a lot of headaches already!